Method for preparing an asbestos fiber product of improved filtration characteristics

ABSTRACT

Asbestos fiber having aluminum sulfate deposited on its surfaces and especially well suited for forming fast-filtering asbestoscement slurries, the preparation of such fiber, and the production of water-laid asbestos-cement products involving the formation of the fast-filtering asbestos-cement slurries utilizing the asbestos fiber having the aluminum sulfate previously deposited thereon. Such asbestos fiber product is preferably dry but can be only partially dry or wet.

United States Patent Stiefken [54] METHOD FOR PREPARING AN ASBESTOSFIBER PRODUCT OF IMPROVED FILTRATION CHARACTERISTICS [72] Inventor:Charles E. Stiefken, Westfield, NJ.

[73] Assignee: American Smelting and Refining Company, New York, NY.

[22] Filed: Oct. 27,1969

[21] Appl.No.: 869,754

CLRSSIFIEE CVCLONE.

ALUMINUM SULFRTE SPRRV q OPEN TOP sctaaw CONVEYOR 1 Feb. 22, 19722,568,023 9/1951 Perry ..1l7/l00 X 2,841,858 7/1958 Owens. ..117/l05.3 X2,885,366 5/1959 ller ..1 17/100 2,886,466 5/1959 ller et a1 ..1 17/1263,014,835 12/1961 Feigley et al... ..117/100 X 3,271,186 9/1966 Sadleret a1. ..1 17/100 Primary Examiner-William D. Martin AssistantExaminer-Mathew R. P. Perrone Attorney-Elwood J. Schaffer and Roger .1.Drew [57] ABSTRACT Asbestos fiber having aluminum sulfate deposited onits surfaces and especially well suited for forming fast-filteringasbestos-cement slurries, the preparation of such fiber. and theproduction of water-laid asbestos-cement products involving theformation of the fast-filtering asbestos-cement slurricn utilizing theasbestos fiber having the aluminum sulfate previously deposited thereon.Such asbestos fiber product is preferably dry but can be only partiallydry or wet.

I OVERSlZE ASBESTOS FIBER FROM FIBER SCREENS DRVING BUCKET CONVEYOR 7Claims, 1 Drawing Figure 1?) f FlBER BlN PRELlMlNFlRY OMPRESS|ON ToCoMPREssmN AND PACKAGING PATENIEDFB22 I972 Emmi.

IIJV ELF! To Q CHARLES E,TIEFKEN K .12.- 7; TOENEH UZOJUxuU NM-LZWWCJUmZwwNUw Emmi ZONE HUME wQPWwQwQ wN wmw o METHOD FOR PREPARING ANASBESTOS FIBER PRODUCT OF IMPROVED FILTRATION CHARACTERISTICS BACKGROUNDOF THE INVENTION 1. Field of the Invention This invention relates toimproving the filtration characteristics of asbestos and moreparticularly to a new and improved asbestos fiber product especiallywell suited for forming fast filtering asbestos-cement slurries, amethod of preparing the new and improved asbestos fiber product, and toan improvement in the method of producing water-laid asbestoscementproducts wherein a considerably faster filtration rate of theasbestos-cement slurry is achieved during the production.

2. Description of the Prior Art Alkali metal silicates and phosphateshave been deposited on asbestos fiber heretofor for improving thefiltration characteristics of the asbestos. High molecular weightpolyacrylamides and naturally occuring guar gum have been added toasbestos-cement aqueous slurries by the asbestos-cement productproducers, for improving the filtration rate of the asbestos-cementslurry. The use of the high molecular weight polyacrylamides and guargum may result in clogging or plugging of the pores or openings of thefelt, screen, perforated cylinder or other porous means employed informing the water-laid web of asbestos-cement. Papermakers alum, Al(SO,,)B3-l8 H 0, and a water-soluble salt of an organic carboxylic acidhaving or more carbons are also known in the 30 prior art for additionto asbestos-cement slurries, as con trasted with deposition on theasbestos fiber prior to forming the slurry, for forming fast drainingslurries, and are disclosed and claimed in U.S. Pat. No. 3,014,835.Although the addition of the alum and the salt of the organic carboxylicacid having 10 or more carbons to the asbestos-cement slurry is reportedto give satisfactory results, there is room for improvement from thestandpoint of speeding up the filtration rate of the asbestos-cementaqueous slurries inasmuch as the faster the draining or filtration rate,the greater the through-put and production rate of the asbestos-cementproducts. Hence it is readily seen that a considerable improvement inthe filtration rate of asbestos-cement slurries should play an importantrole in the economics of the method of producing the asbestos-cementproducts. Further, the requirement of addition of additive materials tothe asbestos-cement slurries by the asbestoscement product manufacturermay put the manufacturer to an inconvenience, trouble and expense whichhe may not be desirous of having, and which would be obviated oreliminated by forming the slurry with asbestos fiber having thefiltrationaccelerating additive previously deposited thereon at theasbestos mill.

SUMMARY OF THE INVENTION In accordance with the present invention, Ihave found that an asbestos fiber product of considerably improvedfiltration characteristics is attained by applying to the asbestos fiberonly, as contrasted with applying to an asbestos-cement slurry, a liquidsolution of aluminum sulfate. After application of the aluminum sulfatesolution onto the fiber the thus-treated fiber is collected forpackaging or other disposition. Although the aluminum sulfatesolution-treated fiber will usually be dried after application of suchsolution and before collecting the fiber, it is not essential to dry thetreated fiber or, if the fiber is dried, to dry it completely. Thedrying of the thus-treated fiber, if desired, can be effected by theapplication of external heat, or by simply allowing it to air dry or byother suitable means. The drying of the treated fiber serves to depositaluminum sulfate solids on the fiber surfaces, the deposited aluminumsulfate solids adhering to the fiber surfaces.

The product asbestos fiber of this invention is composed of the asbestosfiber having the aluminum sulfate deposited on surfaces of the fiber.The fiber is ordinarily composed of a plurality of asbestos fibers ornumerous such fibers intertwined or 75 clumped together in the usualmanner characteristic of asbestos fiber. However, although it isunlikely, a single fiber having the aluminum sulfate deposited on itssurface can, if desired, constitute the asbestos fiber of the product ofthis invention. The aluminum sulfate-treated asbestos fiber of thisinvention when dry will of course contain moisture in an amount which isin equilibrium with that of the surrounding air. As brought out supra,however, the aluminum sulfatetreated asbestos fiber of this inventioncan, if desired, be wet, moist or only partially dry.

After application of the aluminum sulfate aqueous solution to theasbestos fiber and drying of the thus-treated fiber, the fiber can befiberized, i.e., milled, if desired, to further liberate or freeasbestos fiber which is agglomerated together by reason of the aqueousliquid of the aluminum sulfate solution. Such fiberizing of the aluminumsulfate-containing fiber does not adversely effect the considerablyimprovement in filtration rate of the asbestos-cement slurry, and thiswas unexpected and surprising as is was felt that the milling of thefiberizing would dislodge the adherent aluminum sulfate from the fibersurfaces to the extent of reducing materially faster filtration rate.

The asbestos fiber product of this invention is especially well suitedfor use in the production of water-laid cementasbestos products byreason of achieving a considerably improved water filtration rate. Inthe production of the waterlaid cement-asbestos products an aqueousslurry is formed of the cement and the asbestos fibers, and a water-laidproduct is formed from the aqueous cement-asbestos fiber slurry byfiltering or draining the water therefrom. The utilization of theasbestos fiber product of this invention composed of the asbestos fiberhaving aluminum sulfate deposited on surfaces of the fiber per se as thefiber for forming the aqueous cementasbestos fiber slurry, as contrastedwith adding the aluminum sulfate to a previously formed aqueouscement-asbestos fiber slurry with the asbestos fiber free of thealuminum sulfate, attained a considerably faster rate of filtration ofthe water from the water-laid product.

The present invention is eminently well suited for improving thefiltration characteristics of asbestos-cement slurries wherein theasbestos fiber is that normally found in the Province of Quebec, Canada,especially chrysotile fiber found in the Province. However the inventioncan also be practiced on other asbestos fiber as exemplified by amosite,crocidolitc, anthophyllite, tremolite and actinolite.

Any suitable aluminum sulfate is utilizable in accordance with thisinvention for deposition on the asbestos fiber. Thus the aluminumsulfate can be, for example, alum or papermakers alum, i.e., Al (SO -l8H O, Al (SO 'l4 H O, Al (SO )B3-9 H O, or Al (SO,)

The asbestos-cement water-laid products preparable in accordance withthis invention are exemplified by asbestos-cement sheets, boards, pipe,shingles, panels, clapboards, corrugated siding and roofing sheets,tubing, and other products including various special shapes and forms ofthe material.

The aluminum sulfate-treated asbestos fiber of this invention isutilizable in asbestos-cement compositions or products wherein thecement comprises a common hydraulic cement containing, for examplePortland cement or a slag cement. The asbestos cement may also containsilica either as a filler or reactant, and the assorted fillers,pigments, etc., commonly utilized in the industry.

BRIEF DESCRIPTION OF THE DRAWING The accompanying drawing is a flowdiagram for preparing the product asbestos fiber of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The aluminum sulfate solutionis preferably applied to the asbestos fiber by spraying the solutiononto the fiber.

In one embodiment, the spraying may he an atomized spraying of thealuminum sulfate solution onto the asbestos fiber which is suspended inair or moving upwardly in an uprising column of air. In anotherembodiment the aluminum sulfate solution is sprayed onto the asbestosfiber while the fiber is passing through a conveyor, for instance ascrew conveyor.

passes from the discharge end 12 of screw conveyor into fiber bin 13.The fiber is withdrawn from bin 13 through outlet 14, and a minor ormajor portionof the fiber is returned to bin 13 via bucket conveyor 15for purpose of blending. Alterna- The asbestos fiber having the aluminumsulfate solution 5 tively the remaining fiber, or all fiber when norecycling of deposited thereon is preferably dried prior to beingcollected. fiber to bin 13 is employed, from bin 13 is passed byconveyor Less preferably such fiber can be collected in a partially dryor 16 to the preliminary compression screw unit 17 wherein the in a We!state, and the y g p can be Omittedfiber is compressed to a limited orrelatively small extent.

The spraying treatment results in a thin deposit or coating of Frompreliminary compression unit 17 the fiber having the the aluminumsulfate on the fiber. The deposit or coating can aluminum sulfate assole filter aid deposited on and adhered to e a i ntinu an r n indeposit 0r coa gits surfaces is passed via conveyor l8 to thecompression unit Although the amount of aluminum sulfate deposited orwherein it is compressed to the desired finnl extent, nlter coated onthe asbestos fiber can be varied over a wide range, it which thecompressed fiber is packaged. is preferred to deposit on the fiber anamount in the range of IS The test data of Table l which follows, showsthe improveabout 25-50 lbs. of the aluminum sulfate per ton of thefiber, ment in filtration attained by spraying the asbestos fiber withmore preferably about 30-40 lbs. thereof per ton, calculated thealuminum sulfate as potential filter aid or reagant over adas Al,(SOWith the preferred spray application, the aqueding the potential filteraid directly to the asbestos-cement ous solution of aluminum sulfate isof course a sprayable soluy. In ca y g out t e tests, in app ying thepotential filter tion and will usually contain, by weight, about 15-50percent 20 aid to the r, 4T3 asbestos fiber ained from the Black of thealuminum sulfate, preferably about 20-30 percent of e egion o Q ebec Pce, Canada was sprayed with an the aluminum sulfate, calculated as Al(SO aqueous solution of the potential filter aid, dried for 30 In theproduction of the cement-asbestos products, the minutes at 2l2'F. andfiberized by ball milling and doubleaqueous slurry can be formed ofhydraulic cement, for inpass disintegration. The thus-treated fiber wasmixed with Porstance Portland cement, with or without silica, and thetland cement and saturated lime-gypsum water to form an product asbestosfiber, for example product chrysotile asbestos-cement slurry for thefiltration tests. In the tests asbestos fibers of this inventioncomposed of a preferably dry wherein the potential filter aid was addedto the slurry of asbestos fiber having the aluminum sulfate deposited onits asbestos and cement, the addition of the potential filter aid tosurfaces. A water-laid web is then formed from the cementthe slurry wasmade by mixing together the asbestos fiber, ceasbcstos fiber slurry byfiltering off a major portion of the ment, and saturated lime-gypsumwater, then adding the TABLE I Flltln- Reagent Filtration tion Vimprove- Added toasbostos- 'lllnn A tlnns lllllll- Asbestos fibersSprayed onto flbor cement slurry (300.) (80.0.) (perm-lit) r a M I)Control M20104); 47 -8 HS AlCl; M -l .5 Alclagluti NllzCOz All ('i") n4T8 SE-lllb t NluC r r lill l) AlUla Nuolnnthruh Ill (-i--) ll A1915AlClz 5H t) A101; NazOOa 56 ll ll A1013 AlCla plus NnzCOa 23 (+6) t r,t. Ion r0 4T3 SIB-B764 c so "15 25 O4)a 5.) -l 2 54 0 Control .t 42 -1226 4T3 SE-1115 A12(SO4)3 51 3 0 Naoleate 59 2 water of the slurry sothat the fiber and cement are deposited to form a continuous solid wetsheet on a foraminous surface such as, for example, a water absorbentfelt, a moving screen, or a screen-covered perforated cylinder under apartial vacuum. The web thus formed is usually further consolidated anddewatered by applying a partial vacuum to suction rolls or felts or bypressure rolls as the web advances through the machine.

With reference to the drawing, the oversize asbestos fiber from thefiber screens is pneumatically fed through tangentially disposed inlet 5into classifier cyclone 6 wherein the asbestos fiber is cyclonical lyseparated from the dust. The separated fiber is withdrawn from cyclone 6through outlet 7, with the dust being withdrawn from the cyclone throughoutlet 8. The fiber is then conveyed through screw conveyor 9 having anopen top. An aluminum sulfate aqueous solution is sprayed onto theasbestos fiber being conveyed through conveyor 9 by one or more spraynozzle 10. The aluminum sulfate solution is mixed with the fiber by thesubsequent movement of the treated fiber through the screw conveyor.

The thus-treated fiber is then dried by radiant heat applied from abattery of drying lamps 11, such as infrared lamps, mounted above thedischarge end of the open top conveyor 9 and in closely spacedrelationship thereto. Alternatively any suitable or conventional dryingmeans or system can be utilizablc in place of the drying lamps ll. Thedried fiber having the aluminum deposited on and adhered to its surfacesI t potential filter aid and/0r reagant, and mixing further.

In the foregoing Table l, the designations SE-l 1 l5 and "SE-8754" meantwo different samples of the same grade of fiber. As shown by the testdata of Table l the application of the aluminum sulfate to the asbestosfiber increased the rate of filtration of the ultimate asbestos-cementslurry by about 15-25 percent whereas only an about 2-6 percent increasein the filtration rate was obtained by adding aluminum sulfate to theslurry of asbestos and cement. Also as shown by the test data of Tablel, the application to the asbestos fiber of the following potentialfilter aids resulted in no increase in the filtration rate of theultimate asbestos-cement slurry: aluminum chloride plus sodiumcarbonate, sodium carbonate alone. The application of aluminum chloridealone to the asbestos fiber resulted in only a 2 percent increase in thefiltration rate of the ultimate asbestos-cement slurry.

The following test data of Table II also evidences the considerableimprovement in the filtration rate of asbestos-cement aqueous slurriesprovided by utilizing therein as the asbestos fiber that having aluminumsulfate previously deposited on the fiber surfaces as compared with theuse in the slurry of asbestos fiber not having aluminum sulfatedeposited thereon. In the tests, commercial concentrated aqueous liquidalum solution was sprayed on 4T3 and 5R3 asbestos fiber atconcentrations equivalent to 7.9 gallons of the commercial liquid perton of fiber. Such fiber was obtained from ore mined in the vicinity ofBlack Lake, Province of Quebec, Canada.

Various dilutions of the commercial concentrated liquid alum withdistilled water were also sprayed on separate and similar quantities ofthe 4T3 and 5R3 asbestos fiber. The thus-treated fiber was then driedfor minutes at 200 F. followed by fiberizing by ball milling for 60minutes and double-pass disintegrating. Asbestos-cement aqueous slurrieswere then prepared utilizing the fiberized and opened fibers containingthe alum and filtration tests were run on the slurries to determine thefiltration times required to separate the water from theasbestos-cement. The test results are set forth hereafter in Table ll:

What is claimed is: l. A method for preparing an asbestos fiber productof improved filtration characteristics, which comprises:

a. applying to only discrete asbestos fiber a liquid aqueous solutionconsisting essentially of aluminum sulfate; and

b. collecting the thus-treated fiber having the aluminum sulfate as solefilter aid deposited thereon, the thustreated fibers when utilized inasbestos-cement slurries in the production of water-laid asbestos-cementproducts resulting in a considerably increased water filtration rate.

2. A method for preparing an asbestos fiber product of improvedfiltration characteristics, which comprises:

a. applying to only discrete asbestos fiber a liquid aqueous solutionconsisting essentially of aluminum sulfate;

b. drying the thus-treated fiber; and

c. collecting the dry, thus-treated fiber having the aluminum sulfate assole deposit thereon, the thus-treated fiber when utilized inasbestoscement slurries in the production of water-laid asbestos-cementproducts resulting in a considerably increased water filtration rate.

3. The method of claim 2 wherein the aluminum sulfate solution isapplied to the asbestos fiber by spraying the solution onto the fiber.

4. The method of claim 2 wherein the aluminum sulfate solution isapplied onto the asbestos as an atomized spray of said solution whilethe fiber is suspended in air.

' 5. The method of claim 1 wherein the aluminum sulfate is deposited onthe fiber in amount in the range of about 25-50 lbs. of the aluminumsulfate, calculated as AI,(SO per ton of fiber.

6. The method of claim 3 wherein the aqueous aluminum sulfate solutionhas an aluminum sulfate concentration in the range of about 15 to 50weight percent calculated as Al (SO 7. The method of claim 2 furthercharacterized by fiberizing the fiber.

UNITED STA'IFES PATENT OFFICE CERTH lCAl E GI COfiRECl lUN Patent No. 344,138 Dated Februarv 22, 1972 Inventor( s) Charles stiefken It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

r Column 1, line 29, "A12(SO4)B3'18 H20" should read -Alz (SO4)3' l8H20--. Column 2, line 52, "'AlZ (SO4)B3-9 H20" shou] read --Al2 (504)3-9H20--. Column 4, Table I, in the first column heading on the left handside of the table, "Asbestos fibers should read --Asbestos Fibers--; inTable I, the column having the heading "Sprayed onto fiber", the bracketg should be extended upwardly to include the line immediatel above "A1(SO4) in this column; in Table I, the column having the heading"Filtration improvement (percentj', third line from the bottom of theTable, "26" should read --22--. Column 5 line 8, a comma should beinserted after 'alum"? and before "and". Column 6, line 29 .."Al2(SO4)"should read -'-Al2(S04)3---; line 30, "3" should be deleted.

Signed and sealed this l th day of July 1972.

(SEAL) Attest:

EDWARQ M. FL ETC HER, JR. R0 T GOT TSCHALK Attesting OfficerCommissioner of Patents

2. A method for preparing an asbestos fiber product of improvedfiltration characteristics, which comprises: a. applying to onlydiscrete asbestos fiber a liquid aqueous solution consisting essentiallyof aluminum sulfate; b. drying the thus-treated fiber; and c. collectingthe dry, thus-treated fiber having the aluminum sulfate as sole depositthereon, the thus-treated fiber when utilized in asbestos-cementslurries in the production of water-laid asbestos-cement productsresulting in a considerably increased water filtration rate.
 3. Themethod of claim 2 wherein the aluminum sulfate solution is applied tothe asbestos fiber by spraying the solution onto the fiber.
 4. Themethod of claim 2 wherein the aluminum sulfate solution is applied ontothe asbestos as an atomized spray of said solution while the fiber issuspended in air.
 5. The method of claim 1 wherein the aluminum sulfateis deposited on the fiber in amount in the range of about 25-50 lbs. ofthe aluminum sulfate, calculated as Al2(SO4)3, per ton of fiber.
 6. Themethod of claim 3 wherein the aqueous aluminum sulfate solution has analuminum sulfate concentration in the range of about 15 to 50 weightpercent calculated as Al2(SO4)3.
 7. The method of claim 2 furthercharacterized by fiberizing the fiber.